Bullpup refers to a firearm configuration in which the mechanism and magazine are located behind the trigger so there is no wasted space for the butt stock as in conventional designs. This bullpup configuration increases the barrel length relative to the overall weapon length, thus permitting a shorter firearm length for the same barrel length or longer barrel for the same weapon length. Bullpups generally allow for a 25% reduction in weapon length, which allows for better maneuverability in confined spaces.
Being held closer to the body, the bullpup design has the advantage of causing less fatigue to the user's positioning arm when the arm is outstretched for long periods of time. Being more compact and having a shorter length allows for greater close-in weapons usage especially in urban environments. There is also a shorter reaction time advantage in raising a bullpup to fire from a downward pointed direction, a result consistent with a lighter weapon. The bolt may also have to be smaller to be able to fit in the stock, with reduced components, resulting in reduced overall weight.
The main disadvantages of the bullpup firearm are ejection interference in some firing positions, short sight radius, and a higher risk of injury at catastrophic breach failures. Nevertheless, a number of bullpup rifles are now in service all over the world.
Generally, bullpups have their ejection port on the right-hand side and eject spent cartridge casings towards the right. Certain designs, such as the FAMAS (France) assault rifle and the AUG (Austria), overcome this limitation by allowing the bolt and ejection port cover to be swapped, turning the weapon into a dedicated left-handed version. Other bullpups such as the Kel-Tec RFB, the Fabrique National's FN-2000 and the Russian A-91 solve the problem by ejecting forward of the rifle. However, the forward ejecting configurations are all quite complex due to the awkward routing of the ejecting cases.
Downward ejection is used in the FN P-90 by using a magazine that is mounted on top of the barrel which limits the magazine to very short cartridges. Most belt-fed machine guns also feature downward ejection. The Interdynamic MKR was ejecting behind the magazine. However the MKR fired from open bolt due to the limited space for the mechanisms behind the magazine.
FIG. 20 is a perspective view of a prior art side ejecting firearm 120 with the magazine located behind the trigger in a bullpup configuration. Casing ejection is then produced by the ejector located above the magazine, which strikes against the cartridge casing bottom during return of the bolt assembly. The cartridge is tilted laterally by the extractor and ejected through a side eject port 130 in the weapon housing. In simply configured automatic weapons, for example, in the Soviet assault rifle AK-47 (Kalaschnikov), casing ejection is produced through a protrusion fixed on the housing. The bottom of the cartridge casing strikes against this protrusion during return of the bolt assembly.
Other weapons have a casing ejector arranged in the center, so that the casings are ejected upward. For weapons of the bullpup design, a center cartridge ejector is unsuitable, since the casings, as described above, are ejected at the site at which the shooter positions his head against the weapon for aiming.
What is needed to solve the above mentioned problems is to improve the functioning of the downward ejecting bullpup rifle through a simpler, more compact and easier to manufacture ejection mechanism.